Advances in communication technology have transformed the Internet in a true information super highway. Scores of communication networks, shared and private, interconnect with one another to provide traffic paths between users. A shared network provides communication services to all users, such as corporations and individuals, willing to subscribe, and is maintained by a service provider. As the number of users increases, the service provider must invest in new equipment to meet the needs of its customers. This is particularly true if the service provider offers guaranteed levels of service for customers who demand certain levels of bandwidth.
Because capital expenditures are costly and therefore, generally avoided, service providers strive to maximize utilization of their existing resources, while minimizing traffic congestion. One way of achieving this goal is for the service provider to oversubscribe its service to its customers, i.e., reserving fewer resources than the sum of what each user is requesting. The underlying assumption for oversubscription is that the probability of all (or a large proportion of) users requesting service at the same time is statistically low. Therefore, the service provider should be able to expand its user base, while maintaining an acceptable level of service without necessarily expanding its network resources.
In a connection-oriented network, e.g., an Asynchronous Transfer Mode (ATM) network, each user of the network must create a connection to transmit and receive traffic. When the connection is created, some network resources, such as bandwidth, processing power and memory, are allocated and reserved for this connection. This constitutes an agreement between the user and the network's service provider. The service provider must enforce this agreement during the lifetime of the connection. Oversubscription in such an environment is common and relatively straightforward because network resources are reserved prior to the transmission of data.
In a connection-less network, e.g., an IP network such as the Internet, a service provider should also have the ability to reserve network resources for its users, except that a pre-established connection is not utilized. Instead, each packet transmitted from and received by a given user is identified, e.g., encoded, such that the service provider can determine from the packet its priority level and reserve the necessary network resources to enforce the agreement. Oversubscription in a connection-less network environment is complicated because network resources are reserved when traffic flow arrives at the network, and not prior to transmission. If the network is operating at, or near, capacity, the service provider can have difficulties providing promised levels of service for its customers, thereby impacting the quality of service.
For example, if a user wishes to send and receive realtime voice and video data, i.e., Constant Bit Rate (CBR) traffic, the service provider can agree to guarantee a certain level of bandwidth for the user's traffic. The agreed level of guaranteed bandwidth is referred to as a Committed Information Rate (CIR), and data flow within this range would be considered high priority. If the network is oversubscribed, the service provider cannot guarantee that high priority flow will be transmitted in the place of low priority flow, such as Unspecified Bit Rate (UBR) or Best Effort (BE) traffic. Thus, oversubscription can cause serious erosion in a provider's quality of service.
Most oversubscription methods for both connection-oriented and connection-less networks are based on static models that are network specific, or complex statistical models that are generally difficult to implement. In addition, most oversubscription methods cover only a single level of oversubscription.
Accordingly, a need exists for an improved method for oversubscribing bandwidth in connection-oriented and connection-less communication networks. The method should ensure that high priority flow is given precedence over low priority flow. The method should be efficient, highly adaptable and easy to implement in a variety of networks. The method should also provide multilevel oversubscription. The present invention addresses such a need.